Telescopic and optical sighting devices (hereinafter "scopes") are often used on firearms to improve accuracy, target acquisition and low light shooting. Scopes generally allow better accuracy than the conventional metallic or "iron" sights included as standard equipment on most rifles, and rifle owners commonly upgrade their rifles with a scope. Scopes are available in many sizes and magnification levels depending on the requirements of the rifle owner.
Many rifles, however, are not primarily designed for scope mounting; this is often true with military and military surplus rifles. Scope mounting on these rifles often requires machining or drilling/tapping of the receiver to provide a place to fasten a scope base. To avoid the expense of machining, some manufacturers offer aftermarket scope mounts which fasten to the rifle without machining. These no-machine mounts, however, can be somewhat bulky, may interfere with access to the rifle action, and significantly affect both the appearance and heft or balance of the rifle.
Several varieties of the Soviet-designed SKS rifle are commonly owned and commercially available However, the standard SKS rifle does not include scope mounting structure. Attempts have been made to provide an aftermarket side-mounted scope base, but these side-mounted systems are not secure and are easily knocked out of alignment. Therefore, a secure scope mounting structure is desirable on an SKS rifle.
The SKS rifle includes a receiver cover positioned over the receiver assembly, near the rearward end of the rifle. After removing the mounting pin, the receiver cover can be removed from the rifle by pulling the cover rearwardly. The standard receiver cover provided with SKS rifles has a relatively smooth outer surface without any structure to mount a telescopic sight or similar sighting device. Therefore, a rifle owner wanting to use a scope on an SKS rifle must machine or tap the receiver cover and/or add an aftermarket mount to secure a scope to the rifle. Many SKS rifle owners may not want an aftermarket mount, or may not have proper tools or the mechanical ability to perform such modifications to the rifle. Furthermore, SKS rifle owners may not want to alter the original components of the rifle by machining, drilling, or other permanent physical change.
Additionally, the standard receiver cover provided with the SKS rifle has a tendency to move laterally (i.e., to the left or right) as well as vertically when the rifle is moved or fired. Thus, any sighting device attached to the standard receiver cover has a certain amount of inaccuracy due to the movement of the receiver cover. Therefore, it is desirable to provide a replacement receiver cover which is securely mounted to the rifle and does not move laterally or vertically when the rifle is moved or fired.
A standard, commercially available mounting structure for attaching telescopic sights to rifles is an elongated rail having a dovetail cross-sectional shape and means for removably attaching the rail to the rifle. Such rails are commonly referred to as "Weaver rails," and many commercially available scopes and scope mounting rings are designed for mounting thereto. Therefore, it is desirable to provide a Weaver-type rail mounting system on a rifle or other firearm.